Optical fiber technology has been widely utilized in today's telecommunication network. It is also the foundation of a future generation of telecommunication technology which is predicted to revolutionize the way people exchange or obtain information.
One important aspect of optical fiber technology is the interconnection of optical fibers to optoelectronic devices such as semiconductor lasers, photo-detectors, etc, wherein the optoelectronic devices either receive optical radiation from the optical fibers or the optoelectronic devices emit optical radiation into the fibers. A good optical interconnect between an optical fiber and an optoelectronic device requires high coupling efficiency (i.e. low loss of light from the coupling), ease of making the coupling, and low cost for making such an interconnect.
The conventional method for coupling an optical fiber to an optoelectronic device is by active alignment. For example, to couple a semiconductor laser to an optical fiber by active alignment, the laser is first turned on to emit optical radiation. A coupling end of the optical fiber is then placed near a light emitting surface of the laser to receive optical radiation, and a photodetector is placed at the other end of the fiber to detect the amount of optical radiation that is coupled into the fiber. The position of the coupling end of the fiber is then manipulated manually around the light-emitting surface of laser until the photodetector at the other end of the fiber detects maximum optical radiation. Optical epoxy is then applied to both the laser and the coupling end of the fiber so as to permanently maintain the optimized coupling.
A photo-detector can be similarly coupled to an optical fiber by shining laser light into one end of the fiber and manually adjusting the position of the other end of the fiber that is to be coupled to the detector until the detector's electrical response to the optical radiation reaches a maximum. Optical epoxy is then applied to attach the fiber to the detector.
Because the dimensions of the light-emitting surface of a semiconductor laser and the cross-section of an optical fiber are very small, e.g. on the order of 10 .mu.m for single mode fiber, coupling a semiconductor laser to an optical fiber is a task that is usually time-consuming and requires expertise and experience. As for coupling an optical fiber to a photo-detector, even though one may increase the size of the detector to make such coupling easier, increasing the detector size undesirably increases the parasitics of the detector and thus compromises the detector's operating speed and frequency response.
One problem of the above-described optical interconnect is that the alignment between the fiber and the optoelectronic device may suffer misalignment under thermal strain. Such thermal strain occurs when the temperature of the interconnect increases due to the heat generated by the optoelectronic device, the circuits for driving the device, or by various other factors such as the nearby electronic componenets.
It is also not practical to apply the above-described method of active alignment to couple multiple optical fibers to an array of optoelectronic devices that are monolithically formed on a semiconductor chip because the array normally contains a large number of devices that are closely spaced. However, it would be very useful to couple such an array of photo-emitters to such an array of photo-detectors via multiple optical fibers in applications such as local area networks (LANs) which require the coupling of signals in parallel.
It is therefore an object of this invention to provide optical interconnects that mechanically couple multiple optical fibers to arrays of integrally formed optoelectronic devices.